From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael@paquier.xyz>
Cc: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Michael Banck <michael.banck@credativ.de>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: pg_verify_checksums and -fno-strict-aliasing
Date: Thu, 30 Aug 2018 19:37:37 -0400
Message-ID: <12123.1535672257@sss.pgh.pa.us> (raw)
In-Reply-To: <20180830175652.GC15446@paquier.xyz>
References: <1535618100.1286.3.camel@credativ.de>
<alpine.DEB.2.21.1808301325070.32764@lancre>
<7321.1535639966@sss.pgh.pa.us>
<20180830175652.GC15446@paquier.xyz>
Michael Paquier <michael@paquier.xyz> writes:
> On Thu, Aug 30, 2018 at 10:39:26AM -0400, Tom Lane wrote:
>> (The right fix, of course, is to malloc the work buffer rather than
>> put it on the stack.)
> pg_upgrade/file.c is careful about that (5afcd2a), and has a comment on
> the matter, as does pg_standby.c.
> Now, grepping around for "BLCKSZ]", some garbage may have accumulated?
Ah, that's a cute idea for finding trouble spots.
> - entrySplitPage in ginentrypage.c
> - rewind_copy_file_range in file.c
> - _hash_alloc_buckets in hashpage.c
> - pg_prewarm.c
> - blinsert.c
> - pg_waldump.c
> - logtape.c
Some of these are safe, I think, because the buffers are only used as
targets for read() and write(). But some are definitely broken.
My own list of files that seem to have issues is
blinsert.c
generic_xlog.c
ginentrypage.c
hashpage.c
pg_verify_checksums.c
pg_waldump.c
xloginsert.c
The fact that some of these are pretty old and we've not noticed is
not good. It suggests that we don't currently have any compilers in the
buildfarm that under-align char[] arrays on the stack, which seems like
a gotcha waiting to bite us. I wonder if there is any way to persuade
some compiler on a non-Intel box to do that.
Anyway, I'll work on a patch for that, unless you were on it already?
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, michael@paquier.xyz, coelho@cri.ensmp.fr, michael.banck@credativ.de
Subject: Re: pg_verify_checksums and -fno-strict-aliasing
In-Reply-To: <12123.1535672257@sss.pgh.pa.us>
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